Note: Descriptions are shown in the official language in which they were submitted.
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Device and method for cutting plastic products provided in a continuous
plastic band for use in the medical sector
Description
The present invention is directed to a device for cutting plastic products
provided in a
continuous plastic band wherein the single plastic products are connected to
each
other for use in the medical sector, comprising at least one laser, at least
one laser
control system, at least one optical acquisition and data processing unit, and
a quality
control device with an integrated pressure sensor for the detection of
incorrect or not
sufficient laser cuts. Furthermore, the present invention is directed to a
machine for
the production of plastic products, especially the production of filled or
fillable plastic
products for use in the medical sector, comprising the device for cutting
plastic
products provided in a continuous plastic band connected to each other.
Also
disclosed is a method to cut the plastic products in the continuous plastic
band
wherein the single plastic products are connected to each other.
It is known that lasers can be used e.g. to cut, weld or engrave. Different
approaches
have been pursued in the prior art. The patent application DE 102007046142 Al
describes a device with an electronically controllable robot with a laser
cutting head
that can be moved to predetermined reference positions. Another method for
engraving with a laser is described in DE 10148759 Al. In this method the
laser is
focused on the substrate, and the substrate is moved in the x-y axis. Another
method
for welding is described in the patent DE 102005035495 B4.
The US 5 231 262 A application discloses a laser cutting device, comprising a
laser,
a position detection system, an image processor and a laser control system in
form
of mirrors, light-shutters, objective lens and a rotating arm. The US 4 328
411 A
application describes a method to cut amorphous metal through crystallization
with a
laser. Also disclosed is a punching machine in combination with a pressing
mould,
which punches the pre-cut form out of the amorphous metal.
The objective of the present invention is to provide a device, which further
improves
the prior art and allows an increased efficiency when cutting plastic products
provided in a continuous band for use in the medical sector.
This objective is achieved by the present invention by a cutting device as
described
herein and a method for cutting as also described herein.
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Further preferred embodiments of the invention are described herein.
Surprisingly it was found that a device, comprising at least one laser, at
least one
laser control system, at least one optical acquisition and data processing
unit, and a
quality control device with an integrated pressure sensor for the detection of
incorrect
laser cuts has an increased efficiency when cutting plastic products provided
in a
continuous band wherein the single plastic products are connected to each
other for
use in the medical sector.
The functional principle of the inventive device is as follows: An optical
acquisition
unit determines positional data of the plastic products provided in the
continuous
band and connected to each other. The positional data are used to calculate a
cutting
pattern, which is transmitted to the laser control system. In accordance to
the cutting
pattern, the position, intensity and focal point of the at least one laser
beam is
controlled through a focusing optic and a deflection means.
According to the present invention gas lasers, solid-state lasers and/or dye
lasers
can be used. The lasers belonging to the group of gas lasers comprise excimer
laser,
noble gas ion laser, metal vapor laser or molecular gas laser.
The group of excimer lasers includes but is not restricted to H2-laser
(116/123 nm),
Ar2-laser (126 nm), F2-laser (157 nm), Xe2-laser (172 nm), ArF-laser (193 nm),
KrF-
laser (248 nm), XeBr-laser (282 nm), XeCI-laser (308 nm) and XeF-laser (351
nm).
Noble gas ion lasers include but are not restricted to (Ar) -laser (including
¨460 nm,
480 nm, 500 nm, 520 nm), (KW-laser (650 nm) and He-Cd-laser (325 nm, 440 nm).
The group of metal vapor lasers includes but is not restricted to Cu-laser
(500 nm,
545 nm) and Au-laser (310 nm, 605 nm). The group of molecular gas lasers
comprises CO-laser (6-8 pm), CO2-laser (9 pm, 10.6 pm, 11 pm) and N2-laser
(337
nm).
Solid-state lasers can be selected from ruby Cr3+:A1203-laser (694 nm),
Neodymium
glass (Nd:Glass) laser (1062 nm), Neodymium-YAG-laser (1064 nm), Alexandrite-
laser (755 nm), ALGaN/GaN-laser (400-500 nm), InGaAs/GaAs-laser (700-880 nm),
InGaAsP/InP-laser (900-1100 nm) and Pb-Chalkogenide-laser (2,6-30 pm). The
group of dye lasers comprises amongst others stilbenes, coumarins and
rhodamines
covering the whole spectrum from ¨300 nm to 1300 nm.
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In further embodiments the cutting process can be performed parallel,
synchronous
or consecutively by multiple lasers. Preferably the cutting process is
performed by
two lasers, more preferably by three lasers and most preferably by four
lasers. There
is no limit to the number of lasers. The number of lasers can be adapted and
depends on the complexity of the cutting pattern and the size and dimension of
the
plastic products provided in the continuous band. It is also possible to split
the laser
beam with a beam splitter into multiple beams and control each beam
independently
from each other for the cutting process. Preferred are CO2-laser and UV-laser.
In
particular preferred are CO2-laser with a wave length of 9.4 pm, more
preferably with
10.3 pm or 10.6 pm with a preferred output power of 200 W or between 180 W and
220 W respectively. Preferred UV-laser comprise solid-state lasers on the
basis of
Nd:YAG, YLF or Nd:VO4, where by means of frequency conversion with nonlinear
crystals, the third harmonic with a wavelength of 355 nm or in the vicinity
thereof is
generated. These lasers enable an extremely fine focusing of the laser beam,
which
is suited to cut or separate or perforate the narrow connections between the
plastic
components completely or partially.
According to the present invention, a focused laser beam is guided around the
contours of the plastic products provided in the continuous band to melt or
evaporate
the material between the products and/or the continuous band. The Gaussian
intensity distribution of the laser beam cross-section ensures that the laser
radiation
melts the material at the edges and no burr formation occurs. This has the
advantage
that at the edge of the plastic products no sharp edges form that may damage
e.g.
sterile gloves used in the medical field or even lead to cuts to the hand of
the person
working with the cut plastic products. The separation with a laser beam has
distinct
advantages over mechanical separation devices like e.g. punching devices,
because
the use of mechanical devices leads inherently to the formation of burrs or
sharp
edges. The sharpness of the resulting burr and/or the cutting edge is directly
dependent form the hardness/rigidity of the plastic material.
The plastics are preferably selected from the group consisting of polyamides,
polyolefins or copolymers, as well as combinations of such plastics or
copolymers in
the form of composite materials. Preferably the plastic is polyethylene (PE),
even
more preferred is polypropylene (PP) or any other plastic with at least the
hardness/rigidity, tensile strength, torsion module, Young's modulus and/or
melting
range of polypropylene (PP). Any plastic, that is at least as rigid or hard or
even more
rigid or harder as PP can be cut preferably according to the present
invention.
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Further plastics that can be used with the inventive device can be selected
from the
group consisting of or comprising: polyvalerolactones, poly-E-decalactones,
polylactonic acid, polyglycolic acid, polylactides, polyglycolides, copolymers
of the
polylactides and polyglycolides, poly-E-caprolactone, polyhydroxybutanoic
acid,
polyhydroxybutyrates, polyhydroxyvalerates, polyhydroxybutyrate-co-valerates,
poly(1,4-dioxane-2,3-diones), poly(1,3-dioxane-2-
ones), poly-p-dioxanones,
polyanhydrides such as polymaleic anhydrides, polyhydroxymethacrylates,
fibrin,
polycyanoacrylates, polycaprolactonedimethylacrylates, poly-b-maleic acid,
polycaprolactonebutyl-acrylates, multiblock polymers such as
from
oligocaprolactonedioles and oligodioxanonedioles, polyether ester multiblock
polymers such as PEG and polybutyleneterephtalate, polypivotolactones,
polyglycolic
acid trimethyl-carbonates, polycaprolactone-glycolides, poly-g-ethylglutamate,
poly(DTH-iminocarbonate), poly(DTE-co-DT-carbonate),
poly(bisphenol-A-
iminocarbonate), polyorthoesters, polyglycolic acid trimethyl-carbonates,
polytrimethylcarbonates, polyiminocarbonates,
poly(N-vinyl)-pyrrolidone,
polyvinylalcoholes, polyesteramides, glycolated polyesters, polyphosphoesters,
polyphosphazenes, poly[p-carboxyphenoxy)propane], polyhydroxypentanoic acid,
polyanhydrides, polyethyleneoxide-propyleneoxide, polyurethanes, polyether
esters
such as polyethyleneoxide, polyalkeneoxalates, polyorthoesters as well as
copolymers thereof, carrageenanes, collagen, polyhydroxyalkanoates, pectic
acid,
actinic acid, carboxymethylsulphate, collagen, collagen-N-hydroxysuccinimide,
polyacrylic acid, polyacrylates, polymethylmethacrylate,
polybutylmethacrylate,
polyacrylamide, polyacrylonitrile, polyamides, polyetheramide, polyethylene
amine,
polyimides, polycarbonates, polycarbourethane, polyvinyl ketones, polyvinyl
halides,
polyvinylidene halides, polyvinyl ethers, polyvinyl aromatics, polyvinyl
esters,
polyvinylpyrrolidone, polyoxymethylene, polybutylene, polytetrafluoroethylene,
polyolefin elastomers, polyisobutylene, EPDM Rubber, Fluorosilicone,
carboxymethylchitosan, polyethylene terephthalate, Polyvalerate, ethyl vinyl
acetate
copolymers, polysulfones, polyethersulfones, epoxy resins, ABS resins,
silicones
such as polysiloxanes, Polyvinylhalogene and copolymers and / or mixtures of
the
aforementioned polymers as well as laminates and multi-layer systems of the
aforementioned polymers.
Plastic products made of polypropylene have the great advantage over plastic
products made of polyethylene that they can be autoclaved and sterilized at or
above
temperatures of 121 C. This is of particular importance in the medical sector,
where it
is essential to ensure that all germs are killed. Because of the higher
temperatures
necessary to process polypropylene the plastic products have to be cooled down
over a longer distance and/or a longer time before it is possible to cut the
plastic
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products out of the continuous plastic band wherein the single plastic
products are
connected to each other. Moreover, PP is much harder than PE and mechanical
cutting or punching leads naturally to even more sharp burrs and/or cutting
edges.
With the inventive device it is possible to cut plastics with a high
processing
temperature directly after processing. It is not necessary to wait for the
plastics to
cool down nor is it needed to install long conveyer bands to cool the plastic
products
during transportation down to a temperature at which it is possible to cut the
plastic
products. Consequently, it is also preferred to cut plastics that have a high
Young's
modulus and thus tend to form sharp burrs and/or edges when cut or punched
mechanically. Especially preferred is polypropylene, which is regularly
specified with
a melting range between 160 C and 170 C and a Young's modulus of about 1520
N/mm2. Thus, such plastics are preferred which have a melting range above 160
C,
more preferred above 180 C, further preferred above 200 C and especially
preferred
above 220 C and can be routinely autoclaved at or above temperatures of 121 C
without getting deformed. Furthermore, such plastics are preferred which have
an
operating temperature above 100 C, more preferred above 110 C and/or with a
Young's modulus above 1500 N/mm2, more preferred above 1700 N/mm2 and further
preferred above 1900 N/mm2. An especially preferred plastic that can be cut
with the
inventive device is polypropylene and any other plastics, characterised by a
melting
range, tensile strength, torsion module or hardness/rigidity in the range of
polypropylene, wherein "in the range" of is defined as 10% to the
corresponding
value of polypropylene, i.e. a value of -10% to +10% of polypropylene.
The inventive device uses a laser to cut the plastic products provided in the
continuous band of plastic. A cooling line for the hot plastic products is not
necessary, because the laser can cut the hot material or the hot material in
the
process of cooling down respectively, safely and precisely. This is especially
advantageous, when cutting plastic products for the medical sector at elevated
temperatures directly or shortly after the plastic products leave the molding
roll, when
they already start to harden. Additionally, it is possible to perforate the
narrow
connections between the plastic components completely or partially or to
induce
predetermined breaking points making it easier to separate the plastic
products from
each other. This is especially advantageous when the plastic products are made
of
polypropylene, which is extremely tenacious after cooling down making it
difficult to
separate the plastic products manually without any further mechanical aid e.g.
a
scissor.
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Therefore, the inventive laser cutting device is especially useful for cutting
warm or
hot polymers and plastics, i.e. cutting polymers or plastics with a
temperature of at
least 60 C, preferred at least 80 C, further preferred at least 100 C, more
preferred
at least 115 C, more preferred at least 125 C, even more preferred at least
135 C,
further preferred 145 C and more preferred at least 155 C, whereby plastics
and/or
polymers can be cut even at temperatures from 200 C to 250 C. Furthermore, the
device according to the invention is preferably used to cut plastic products
that are in
the process of cooling or heating, wherein the temperature of the segment to
be cut
is different at the beginning of the cutting process in comparison to the
temperature
at the end of the cutting process. The word "segment" is to be understood as
the
section for example in a continuous belt that is recognized in a work cycle by
the
optical acquisition unit and were the cutting pattern is defined. The laser
cutting is
very accurate even when a temperature gradient exists, i.e. temperature
changes
during cutting in the plastic product or the plastic segment respectively. The
inventive
device acquires and processes the cutting pattern for the plastic products
correctly in
a temperature range from ¨ 100 C to + 300 C. Any changes in the temperature of
the plastic up to 1 C per second can be acquired and processed by the
inventive
device. This includes also changes in consecutive cutting patterns and cutting
modes
as well as for changing plastic materials during the cutting of a cutting
pattern or for
consecutive segments and cutting patterns.
The term "cutting" or "laser cutting" as used herein shall be understood as
cutting
through plastic material with a laser beam, preferably polypropylene and
similar
polymers or polyethylene, this also includes perforating, i.e. alternating
parts of cut
through and uncut parts as well as cutting partially through or thinning
parts, in the
meaning that the material at the cutting point is not completely cut through
but only
the thickness is reduced, i.e. the material bonding still exists, but can be
separated
mechanically with less force. Thus, the term "cutting" or "laser cutting"
describes
cutting completely through the plastic material along the whole cutting
pattern or only
at specific points of the cutting pattern as well as perforating the plastic
material
along the whole cutting pattern or only at specific points of the cutting
pattern, i.e.
completely cut through parts alternate with uncut parts.
The term "cutting pattern" is to be understood as the totality of all parts to
be cut,
which are acquired by the optical acquisition unit in one detection step. The
cutting
pattern can be positioned in a segment of a continuous band of interconnected
plastic products. Thus, if it is intended to cut plastic products in a
continuous band or
belt of interconnected plastic products, the optical acquisition unit
gradually acquires
a part (i.e. segment) of the continuous band or belt of interconnected plastic
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products, which is fed to the inventive device and then is cut according to
the cutting
pattern. The cutting pattern comprises the plastic products, acquired through
the
optical acquisition unit, which are usually three-dimensional and lie above
and below
the plane level and are defined through the continuous band or the continuous
belt,
which can comprise further user definable and thus predefined information
concerning the cutting mode. The optical acquisition unit can detect for
example,
where the cutting is to be performed. The mode of cutting (completely,
partially,
perforating, etc.) can be predetermined by the user. Alternatively or
additionally the
optical acquisition unit can detect respective markings, which do not only
give
information where the cuts are to be made but also the mode of cutting can be
included as information. Naturally a combination of the aforementioned is
possible,
thus a mix of predefined patterns and automatic detection of the cutting mode
and/or
cutting pattern is possible. Instead of a continuous band or a continuous belt
it is also
possible that single units or only parts of the continuous band, i.e. isolated
segments,
are detected by the optical acquisition unit.
The cutting pattern and eventually the cutting mode is determined anew by the
optical acquisition unit before cutting a specific section, or specific part
of the
continuous band or the continuous belt, thus it is possible to handle various
cutting
patterns and cutting modes in random order. This is a distinct advantage over
mechanical cutting and/or punching processes. The mechanical punching or
mechanical cutting tool are determined for a defined cutting pattern or
defined cutting
mode and cannot adapt to changes in alternating segments with different
cutting
patterns and cutting modes. The inventive laser cutting device can handle up
to ten
different cutting patterns with different cutting modes, which is impossible
to achieve
with a mechanical cutting or punching tool. Even if different punching or
cutting tools
are used, there are still only a limited number of patterns that can be
handled. The
inventive device is independent of the exact cutting pattern, i.e. is not
restricted to a
specific pattern but can detect and handle any cutting pattern.
The cutting pattern is determined through suitable markings, which are
detected by
the optical acquisition unit. This can include colored markings, spatial
markings as
well as radioactive markings.
Colored markings include for example, colored markings in the visible range,
infrared
range or UV range and can be incorporated or attached to the plastic. This
extends
also to other materials which can be incorporated or attached to the plastic
and are
distinguishable from the plastic material such as thin filaments, wires or
micro
particles. Spatial markings on the other hand can be realized as elavations,
dents or
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holes in the plastic material. Radioactive markers are radioactive substances
incorporated or attached to the plastic material, wherein a radioactively
labeled
substance or solution in the plastic product may serve as a marker.
The data processing unit determines which parts of the cutting pattern are to
be cut
by the laser completely, or are only perforated, thinned and/or are not to be
processed. Thus, the laser is capable of cutting specific parts completely,
perforate
them, reduce the thickness of the material to a specific degree and/or ignore
specific
parts, all within the limits of the detected and/or predetermined cutting
pattern by the
optical acquisition unit, depending on which mode of cutting was predefined by
the
user or a marking in the cutting pattern or a segment respectively. The laser
is under
the control of the data processing unit and is guided according to the cutting
pattern
detected by the optical acquisition unit and the predefined cutting mode.
The use of the laser beam for accurate cutting of the plastic products is
dependent
from the optical acquisition unit, which determines positional data of the
interconnected plastic products provided in the continuous plastic band. The
positional data can comprise information about the forms, sizes, shapes,
geometric
forms, laser markings, shadow projection, color recognition, light / dark
zones or
reflections which are detected by the optical acquisition unit.
In a preferred embodiment the optical acquisition unit comprises a camera. In
another preferred embodiment a laser scanner is used together with a detector
to
determine positional data by measuring the interconnected plastic products
provided
in the continuous plastic band. The laser can be diverted by a mirror system
to depict
a complete surface profile of the plastic products.
The positional data are transmitted to a data processing unit, e.g. a
programmable
micro processor, where they are further processed. The term "processed" is to
be
understood in the way that the actual determined positional data is compared
with
positional data stored in the data processing unit. For each combination of
positional
data a cutting pattern is stored in the data processing unit, which is
transmitted to the
laser control system to control the laser.
This has the advantage that a precise dimensional accuracy of the plastic
products
provided in the belt is not required, because the optical acquisition unit
detects the
respective actual state of the plastic products. Particularly for the
manufacture of
plastic products usually high temperatures are used. The resulting temperature-
dependent expansion and/or shrinking of the plastic has made an e.g.
mechanical
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punching only possible at fixed lower temperatures. The use of the inventive
device
eliminates this problem and the plastic products can be cut accurately at
different
temperatures. Moreover, it follows that when cutting various different plastic
products, a complicated conversion of the device is not necessary, because
only the
cutting patterns must be changed for the positional data.
In another preferred embodiment the positional data are not compared with the
stored positional data, but the data processing unit calculates the respective
cutting
pattern from the acquired positional data and transmits the calculated cutting
pattern
to the laser control system to control the laser.
In a further preferred embodiment positional data as well as cutting patterns
are
stored, which are corrected by the respective actual positional data, leading
to an
adapted cutting pattern which is transmitted to the laser control system to
control the
laser.
The laser control system consists preferably of a controllable focusing optic,
a
controllable deflection means and a beam-forming means. In this context the
term
"controllable" is to be understood that the focusing optic and the deflection
means
can be controlled with the cutting patterns calculated by the data processing
unit and
further that the data are transmitted in a suitable format. The beam-forming
means
collimates the laser beam and reduces the divergence of the beam for the
purpose of
a better focusing. In accordance with the determined positional data, the
position of
the focus and intensity of the focal point of the at least one laser is
controlled by a
controllable focusing optic and a controllable deflection means. If more than
one
laser is used preferably each laser is controlled by another laser control
system.
In an embodiment the laser control system comprises a beam-forming means,
which
collimates the laser beam, a telescopic lens system, which reduces the
divergence of
the beam for the purpose of a better focusing, a mirror deflection system,
which
guides the laser beam in two- or three-dimensions around the interconnected
plastic
products according to the predetermined cutting pattern, a focusing optic,
which
focuses the laser beam such that the plastic material is evaporated during the
movement of the laser beam and a software-controlled electronics, which
converts
the data for the cutting pattern in mirror movements.
In a preferred embodiment, the controllable deflection means is a galvanometer
scanner, deflecting the direction of the laser beam with mirrors. In more
preferred
embodiments, the galvanometer scanner deflects the laser beam over two or more
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mirrors. Depending on the geometric properties of the plastic products one or
more
controllable deflections means can be used. In a preferred embodiment, no
relative
movement takes place between the plastic product and the laser optics, i.e.
the laser
optics is fixed and immovable, and the laser beam is controlled only by the
controllable deflection means.
In another embodiment the laser beam is not deflected by a controllable
deflection
means, but the laser optics or a part of the laser optics is moved relative to
the plastic
product to perform the cutting process. The term laser optics comprises all
the
components necessary for forming, focusing, controlling or amplifying the
laser
beam. For example, only the lens and the mirror system can be moved, or only
the
lens, or only the mirror system or the entire laser optics relative to the
plastic product.
In a particularly preferred embodiment the laser beam is controlled by a
movable
controllable deflection means. The term movable in this context means that the
controllable deflection means can be moved in the x, y and z axis. This
ensures that
the laser beam can also reach and cut areas which are difficult to access.
A further advantage is that the controllable deflection means can also be used
to
simultaneously label the ampoules, thus cutting and labeling is done in one
work
process.
The focusing optic is preferably a lens or a mirror, more preferably a convex
lens or a
focusing concave mirror. The concave mirror provides the further advantage
that
each laser wavelength can be focused on the same point without having to use
special optical materials.
In one embodiment, the device comprises a conveying unit for the
interconnected
plastic products provided in the continuous band. This conveying unit consists
preferably of a feeding-in device that pulls the interconnected plastic
products
provided in the continuous band under the laser and the optical acquisition
unit. This
allows a high throughput and a full automatic cutting of the plastic products
provided
in the continuous band.
In other embodiments the conveying unit is a conveyor belt on which the
interconnected plastic products are transported.
One of the significant advantages of laser separation of plastic products,
e.g.
ampoules, bags or other cavities is to create a fused edge as opposed to a
sharp
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ridge after mechanical separation. This is especially important when cutting
plastic
products for use in the medical sector because a sharp ridge may cause damage
to
sterile gloves or may even injure the hand of the doctor or of the hospital
staff when
using such ampoules. Mechanically cut plastic products have always sharp
ridges
due to the fact that at the side where the cutting blade leaves the cut line a
sharp
ridge will occur.
The conventional laser cutting process with a fixed beam and focusing through
a
nozzle for processing gas may also lead to burrs on the edges. It is better to
cut the
ampoules with a movable beam, e.g. with a galvo scanner, because this method
can
be carried out more precisely by fine tuning of laser parameters and beam-
forming
elements, such as telescopes and lenses and scanner movements so that the
edges
are fused at the joints. To achieve this, a sensor and a control system are
required as
provided in the present invention.
However, even with this kind of separation it is possible that the cut plastic
products,
e.g. ampoules, are not separated with fused edges. This is the case when a
barely
perceptible sharp ridge holds the ampoules together. When the ampoules are
then
finally separated, the sharp ridges still remain. Such sharp ridges can be the
result of
slight power fluctuation of the laser or a barely detectable variation in the
beam
direction.
Since the ampoules are provided within a pack of ampoules with very narrow
connections, the quality of the laser cut can usually only be evaluated with a
very
complex image recognition system and special cameras. Such a system slows down
the whole manufacturing process, is inherently expensive and prone to
malfunctions
and cannot easily be integrated in existing systems.
Consequently, the inventive device further comprises a quality control device
with an
integrated pressure sensor for pressing out the cut plastic products. The
interconnected plastic products provided in the continuous plastic band are
preferably not separated completely by the laser from the residual material,
i.e. the
framework, so that the cut plastic products can be transported within the
surrounding
material until the final separation takes place. During the laser cutting,
precisely
defined narrow connections are left between the plastic products and the
surrounding
residual material. For the final separation step the plastic products are
transported
under the quality control device with an integrated pressure sensor. A stamp
with the
form of the ampoule pack or a stamp with a certain number of pins which hit
predefined locations of the single plastic product or of a section of the
continuous
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plastic band, i.e. an adapted stamp, presses the plastic products and
especially the
material between the toggle parts of the ampoules, i.e. the material between
the neck
regions of neighboring ampoules, out of the residual surrounding material. If
the
pressure or force necessary to push the ampoules out of the surrounding
material
and/or the material between the toggle regions exceeds a predefined first
adjustable
value, this is an indication that the plastic products are not sufficiently
separated and
are still connected with the surrounding material, i.e. are still connected to
the belt or
to each other.
Instead of a stamp which actually hits the plastic products or units or
bundles of
plastic products in order to separate them, a gas blow such as an air blow or
multiple
gas blows generated by one or a plurality of nozzles can be used to put a kind
of gas
blow pressure on the plastic products or units or bundles of plastic products.
Thereby the single gas blows are generated with a defined pressure which again
indicates the quality of the laser cut by determining if the gas blow or the
gas blows
were sufficient to separate the single plastic products or units or bundles of
plastic
products. Instead of a gas the skilled person may also use a liquid such as
water for
the same purpose.
Thus, the quality control device with an integrated pressure sensor is
directed to
pressing the laser cut plastic products out of the surrounding residual
material of the
continuous band thereby generating single plastic products or units of plastic
products which are still attached to each other but already perforated
preferably by
the laser used in the cutting device so that the separation can be done easily
without
forming sharp ridges. This is usually performed with an adapted mould having
the
form of the ampoule or ampoule packs. Additionally, narrow stamps can be
included
that push out the residual material between the toggle parts, i.e. the area
between
the neck regions of two adjacent ampoules. If a predefined first adjustable
value is
exceeded, then the laser cutting was not sufficient and the plastic products
are
collected separately. This has the advantage that insufficiently cut plastic
products
can be separately collected from the correctly cut plastic products and then
proceeded later again and thus are not lost as waste. Thus in one embodiment
the
quality control device with an integrated pressure sensor consists of a mould
adapted
to the form of the ampoules, which presses the plastic products precisely out
of the
surrounding residual material.
Furthermore, the quality control device with an integrated pressure sensor can
control the quality of the laser cut, i.e. the quality of the intended
separation, by
measuring the resistance and/or force that is necessary to press the plastic
products
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out of the surrounding residual material. The pressure/force necessary to push
the
ampoules out of the surrounding material and/or the toggle parts of the
ampoules, i.e.
the material between the neck regions of neighboring ampoules, gives direct
information on whether the laser cut did successfully melt the material at the
edges
so that no sharp burr formation has occurred.
The applicant has found when laser cutting, for instance, polypropylene
ampoules
that the following applies:
= If the pressure sensor does not register any resistance, the ampoules are
separated correctly and the edges are completely fused around the ampoules
= If the pressure sensor registers a resistance up to 0.5 N to push the
ampoules
out of the surrounding residual material, then only a negligible ridge has
formed and the use of the ampoule is safe.
= If the pressure sensor registers a resistance over 0.5 N to push the
ampoules
out of the surrounding residual material, then a significant sharp ridge has
formed and the ampoules are possibly harmless and will be sorted out.
Thus, if the required pressure necessary to push the plastic products such as
bags,
bottles, cylinders, ampoules or other cavities out of the surrounding material
and/or
the toggle parts of the ampoules, i.e. the material between the neck regions
of
neighboring ampoules exceeds a second threshold but is still under the first
threshold, this gives an indication that the laser cut is unsatisfactory and
potentially
harmful formation of sharp ridges or burrs in the plastic product has
occurred.
In a further embodiment, the quality control is performed at the material
between the
toggle parts, i.e. the area between the neck regions of two adjacent ampoules.
Thus, the force required to push the plastic products out of the surrounding
residual
material provides information on whether the plastic product was cut
correctly, i.e. the
plastic products can be pushed out of the surrounding material or not.
Furthermore,
the required force indicates, whether the ridges are safe or if any sharp
ridges have
formed that may be potentially harmful.
Having described the inventive quality control device with an integrated
pressure
sensor it is clear to the skilled artisan that the exact first and second
values or
thresholds for the pressure/force depend on factors such as the kind of
plastic to be
cut, the thickness of the material, the temperature at which the cut is
performed, the
output power for the lasers and/or the geometry or size of the plastic
products and
the like. It is within the scope of the skilled artisan to determine through
minimal
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14
experimentation, which pressure or force threshold is indicative for the
plastic
products in the continuous band. Thus, it is not complicated and even not
inventive
to find the right pressure range which indicates for the given plastic product
a
faultless cut or an inacceptable cut so that adjustment of the laser has to be
performed.
In another embodiment, the quality control device with an integrated pressure
sensor
determines the quality of the laser cut by applying an underpressure to the
plastic
product, such as the ampoule, the ampoule pack and/or the toggle region, i.e.
the
material between the neck regions of the ampoules. The mode of action is
similar to
the above described embodiment, however, it is not the force measured that is
required to separate the ampoule, the ampoule pack and/or the toggle region
from
the surrounding residual material. Instead the quality control device with an
integrated pressure sensor measures the force required to apply a certain
under-
pressure such as a certain vacuum.
While the pressure or force is applied from the above to the upper side of the
single
plastic products or the pack or bundle of plastic products, the underpressure
or
vacuum is applied from below the single plastic products or the pack or bundle
of
plastic products in order to separate the single plastic products or the pack
or bundle
of plastic products from the continuous plastic band and from the other single
plastic
products or the other packs or bundles of plastic products.
In a third embodiment of the invention the quality control device with an
integrated
pressure sensor applies a pulling force which can be determined in order to
assess
quality of the laser cut. Such a pulling force can be applied through means
which
grip the single plastic products or the pack or bundle of plastic products and
separate
them from the continuous plastic band and from the other single plastic
products or
the other packs or bundles of plastic products. The force required to separate
the
single plastic products or the pack or bundle of plastic products can be
measured
and is also an indication for the quality of the laser cut in order to assess
if the laser
cut was faultless or not sufficient.
Consequently according to the present invention it is not important if the
separation
of the single plastic products or the single packs or single bundles of
plastic products
is conducted by a pushing force such as pressure, or a pullin force or an
under-
pressure such as vacuum.
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In a further embodiment, the device comprises a system to compensate for long-
term
drift effects of the laser beam and the controllable deflection means. This
may occur
due to changes in temperature, humidity, exposure to vibration, mechanical
stress
and aging of components and can affect the precision of the laser beam
negatively.
The system to compensate for long-term drift effects of the laser beam ensures
that
the precision of the laser is always optimal, reducing production kisses, due
to
maintenance of the device, to an absolute minimum.
In one embodiment, a thermal imaging camera is used, to register the selective
heating on a material surface lying outside of the cutting pattern, but still
within the
range of deflection of the mirror system of the controllable deflection means.
The
selective heating results by directing the beam for a short time on this
material
surface for a specific length of time. These short-term heating can for
example be
performed while the feeding-in device pulls the next interconnected plastic
products
provided in the continuous band under the laser and the optical acquisition
unit. The
thermal imaging camera compares the position on the receiver with previously
programmed set/designed positions. The data collected is then transmitted to
the
laser control system to correct and adjust the cutting pattern. This control
mechanism
can take place both in or before each cutting process or at certain predefined
intervals. The thermal imaging camera can also determine simultaneously the
temperature of the heated material surface and conclude from this data on the
laser
power used for cutting the plastic products. A decrease in laser power can
then be
adjusted accordingly.
In another embodiment a band lying outside of the cutting pattern, but still
within the
range of deflection of the mirror system of the controllable deflection means,
is drawn
along within or outside of the plastic band, whereby the laser removes an
amount of
the material in the band in the form of a point. A camera compares the
position of this
point with a programmed reference point and any deviations are transmitted as
correction data to the laser control system, similar to the process described
above.
The interconnected plastic products for use in the medical field provided in
the
continuous plastic band are preferably bottles, bags or containers, and even
more
preferred ampoules. Furthermore, medical devices or parts of medical devices
can
be cut according to the invention, such as syringes, vials, hollow fibers for
dialysators
or parts of powder inhalers.
Particularly advantageous is the use of the device when cutting multi-layer
plastic
products, such as those produced via co-extrusion blow molding. These multi-
layer
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plastic products combine the positive properties of different plastics
together and are
usually characterized by a barrier layer that is arranged between two carrier
layers,
which are connected together by a bonding agent. Preferably, these multi-
layered
plastic products are used in applications where improved barrier properties
are
needed to gases. Mechanical cutting methods have particularly problems with
the
joints of the multilayer plastic products. At the joints the barrier layer is
naturally not
very pronounced and there is an increased risk that the barrier layer is
interrupted by
the mechanical cutting in those areas. The inventive device has the advantage
that
the individual layers of the multilayer plastic products are fused together at
the joints
and along the edges during cutting with the laser. Consequently, the barrier
properties of the joints, edges or seams remain intact and are even improved
in
comparison to mechanical cutting methods.
The process for separation of plastic products provided or surrounded by
plastic can
be applied and performed similar in principle with the described laser-control
system
with other plastic products such as consumer goods or industrial parts.
In a particularly preferred embodiment, the inventive device is operated in
combination with a device, producing plastic products, under the BFS process
(blow-
fill-seal process). Such devices are well known and are described, for example
in the
patent EP 1626903 B1.
The inventive device is particularly advantageous for cutting plastic ampoules
interconnected, joined together and/or linked together. These ampoules can
e.g. be
filled by the BFS process (blow-fill-seal process) but also empty ampoules can
be
processed. When plastic ampoules are manufactured under the BFS process (blow-
fill-seal process), the ampoules leave the filling machine as rows of
interconnected,
joined together and/or linked together ampoules in a continuous band. In this
continuous band one row of interconnected, joined together and/or linked
together
ampoules is followed by the next row of ampoules and all rows are embedded in
the -
continuous band and surrounded by the residual plastic material. In order to
produce
as many ampoules within the continuous plastic band as possible, the ampoules
are
arranged very close together and thus the separation of the ampoules is very
difficult.
This is especially true for the toggle portion at the neck of the ampoules.
The toggle
portion at the neck of the ampoules is a critical area during mechanical
punching as
there is only a very small area that has to be cut out precisely and often
only a partial
separation can be achieved. Thus there is the constant risk when opening or
separating a single ampoule that the neighbor ampoule is opened accidentally,
due
to the incomplete separation between the toggle portions of the ampoules. The
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inventive device can separate this portion of the ampoules safely without the
risk of
damaging the opening of the ampoules.
Ampoules in the medical field are usually provided as packs, i.e. a certain
number of
interconnected ampoules are punched out mechanically out of the continuous
band.
However, especially ampoules made of polypropylene tend to develop a sharp
ridge
when cut out mechanically or when one ampoule is separated manually from the
ampoule pack.
In contrast to mechanical punching, cutting with the inventive device has the
following advantages. The plastic ampoules are not required to cool down and
can
be cut at higher temperatures. Differences in the size of the ampoules which
are
inherent and cannot be avoided when manufacturing ampoules at high
temperatures
and the shrinking process of the ampoules when cooling down are detected by
the
device and the laser beam is adjusted accordingly. Furthermore, when cutting
with
the laser, the formation of sharp ridges and/or burr formation are avoided and
the
ampoules can be provided by the laser with perforations or breaking points
between
or in the plastic products, making them easier to separate from each other.
The combination of the inventive device with a machine for the production of
plastic
products under the BFS process (blow-fill-seal process) is especially
advantageous,
because there is no longer the need for establishment of a cooling line and
the
plastic products can be cut at higher temperatures immediately after
production.
Together with the above-mentioned advantages, this leads to increased
efficiency,
safety and economy.
The present invention also comprises an inventive method for cutting
interconnected
plastic products for use in the medical sector provided in a continuous band
of plastic
which comprises the following steps:
a) Providing interconnected plastic products embedded in a continuous band of
plastic,
b) Determining positional data for the interconnected plastic products
embedded
in the continuous band of plastic through an optical acquisition unit and
calculation of a cutting pattern through a data processing unit,
c) Controlling the laser by means of a laser control system, consisting of a
controllable focusing optic, a controllable deflection means and a beam-
forming means, wherein in dependence of the determined positional data the
position and intensity of the focal point of the at least one laser is
controlled,
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d) Cutting the interconnected plastic products provided in a continuous band
of
plastic according to the calculated cutting pattern.
In a preferred embodiment the plastic products or packs of plastic products
are cut at
temperatures of the plastic products or packs of plastic products of 60 C to
155 C
In further embodiments the method can further comprise one of the following
steps
e) ¨ e"):
e) Performing a quality test by means of a quality control device with an
integrated pressure sensor, which measures the force required to push out the
cut plastic products or packs of cut plastic products.
e') Performing a quality test by means of a quality control device with an
integrated pressure sensor, which measures the underpressure required to
separate the cut plastic products or packs of cut plastic products.
e") Performing a quality test by means of a quality control device with an
integrated pressure sensor, which measures the pulling force required to
separate the cut plastic products or packs of cut plastic products.
Thus, by means of the integrated pressure sensor, the force, under pressure,
pulling
force or any other such force is measured, which is required to separate the
plastic
products from the surrounding residual material. A
pressure or force or
underpressure (such as vacuum) below a certain value (e.g. value A) indicates
a
proper and faultless cut without sharp ridges, while a pressure or force or
underpressure above a certain value (e.g. value B) indicates an improper and
faulty
cut so that the plastic products cannot be separated or cannot be separated
easily or
cannot be separated without forming sharp ridges. A
pressure or force or
underpressure between the value A and value B indicates an insufficient cut
where
the plastic products can still be separated but might have sharp ridges.
Depending
on the plastic product, the kind of plastic used and the use of the plastic
product in
medicine, the cut plastic products obtained within the range between value A
and
value B might be sold as proper medical products or might be discard as
unrectifiable
rejects. Moreover depending on the plastic product, the kind of plastic used
and the
use of the plastic product in medicine the value A can be identical or almost
identical
to value B.
In a preferred embodiment, when the force to separate the plastic products
from the
surrounding material reaches a first predefined adjustable value, this
indicates that
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the plastic products are still connected to the belt and have not been
separated
successfully, i.e. the force was not sufficient. This also implies that when
this first
threshold or first value has been reached, no further force is applied to
separate the
plastic products. This is important, because if the plastic products are still
tightly
connected to the surrounding residual material, applying an unlimited amount
of force
could lead to damage to the belt and the following plastic products, e.g. by
overstretching the (hot) belt.
Furthermore, it is possible to predefine a second value/threshold which is
under or
below the first value. If the force required to separate the plastic products
from the
surrounding residual material exceeds this second value but is still under the
first
value, the plastic products were separated successfully, but this is an
indication for
an unsatisfactory and potentially harmful formation of sharp ridges or burrs.
If the
required force stays under this second value/threshold, then the quality of
the laser
cut is satisfactory and there is no risk of sharp ridges and/or burrs.
As described above it is clear to the skilled artisan that the exact first and
second
values or thresholds for the pressure/force depend on factors such as the kind
of
plastic to be cut, the thickness of the material, the temperature at which the
cut is
performed, the output power for the lasers and/or the geometry or size of the
plastic
products and the like. It is within the scope of the skilled artisan to
determine through
minimal experimentation, which pressure or force threshold is indicative for
the
plastic products in the continuous band. Thus, it is not complicated and even
not
inventive to find the right pressure range which indicates for the given
plastic product
a faultless cut or an inacceptable cut so that adjustment of the laser has to
be
performed.
Brief description of the figures
Figure 1
View A:
Top view on a belt or continuous belt with interconnected plastic ampoules
(only
three ampoule strips are shown).
View B:
Side view of "View A" (left side). Shown are the ampoule bottoms of an ampoule
strip. The dashed lines show schematically a snapshot of the laser beams.
CA 02790158 2014-07-28
19a
View C:
Side view of "View A" (viewing direction in front). Shown are three ampoule
strips in
the belt.
Figure 2
Schematic side view of an embodiment for cutting interconnected plastic
ampoules
Each strip contains twenty ampoules, which are each interconnected to the rest
of
the surrounding material as well as with the neighboring ampoules on the sides
and
the toggle region. The laser cuts four ampoule packs with five ampoules each
out of
the ampoule strip containing twenty ampoules. This means that the two
outermost
ampoules in the ampoule strip are still connected to the surrounding material
via
some narrow connections; however, the connections between the ampoule packs,
i.e. after every fifth ampoule, are separated completely from each other. The
connections between the ampoules within the ampoule packs are perforated,
which
makes it easier to manually separate the ampoules from the ampoule packs. The
material between the toggle regions of the ampoules are cut out completely and
the
upper edge of the ampoules are separated from the rest of material with the
exception of some narrow connections. In this step, the bottoms of the
ampoules of
the next ampoule strip are separated from the surrounding material, again with
the
exception of a few narrow connections. The reason behind this is the ampoule
geometrics, because the laser beams cannot reach the ampoule bottoms in the
same
work step. Consequently, the ampoule bottoms are separated in the previous
work
step. In the current work step the remaining sides of the ampoules packs are
cut and
the bottoms of the next ampoules are cut.
In a preferred embodiment an ampoule belt (1) is pulled and positioned by a
feeding-
in device (2) under at least one controllable deflection means (5) and an
optical
acquisition unit (5a). The optical acquisition unit (5a) acquires the
positional data of at
least one ampoule strip (II) and the data processing unit calculates from the
positional data a cutting pattern for cutting the ampoules (III) individually
or in packs
of several ampoules out of the at least one ampoule strip (II). The at least
one
focused laser beam (IV) is modified by the beam-forming means (4), such that
the
laser beam is suitable for separating the ampoules (Ill) through evaporation
of the
material between and/or around the ampoules. The controllable deflection means
(5)
and the controllable focusing optic (5b) control the at least one focused
laser beam
(IV) according to the cutting pattern calculated by the data processing unit,
to cut the
ampoules individually or in packs of several ampoules. After the cutting
process the
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ampoule belt (1) is. pulled further by the feeding-in device (2) and the next
ampoule
strip (II) is positioned under the controllable deflection means (5) and the
optical
acquisition unit (5a). The cut ampoules (III) are still located in the ampoule
belt (1)
and are now positioned under the quality control device with an integrated
pressure
sensor (7) and the knife for separating the strips (8). The quality control
device with
an integrated pressure sensor (7) and the knife for separating the strips (8)
are
triggered and the separated material between the toggle parts is collected in
a
separate container (14). The ampoules (III) are now separated completely from
the
ampoule belt (1) and are transported in an upright position over a slide to an
external
transport route (9) for further processing. The knife (8) separates the
residual
material (10) of the stripe from the belt and collects the residual material
in the
container (15). When the quality control device with an integrated pressure
sensor (7)
is triggered to press the ampoules (III) out of the belt it simultaneously
measures the
required pressure. If one or more ampoules are not separated as planned, then
the
required pressure to press the ampoules (III) out of the belt exceeds a
previously
adjustable threshold value, whereby the flap (11) is opened and the residual
material
with the filled ampoules (12) is dropped in the container (16). If the laser
cutting
device falls out completely, then two flaps (13) are triggered and the feeding-
in
device (2) transports the residual ampoule belt (1) uncut out of the device
for later
cutting.
In another embodiment the inventive device separates container products from a
framework and/or among each other and consists of at least one laser with at
least
one laser control system and at least one optoelectronic system for image
recognition and image processing, which determines the position of the
container
products in the framework and/or among each other and transmits these data to
the
at least one laser control system, whereby the at least one laser and/or laser
beam is
controlled such that the container products are separated from the framework
and/or
among each other. The other described inventive embodiments and examples in
this
application apply advantageously also on this embodiment.
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21
The present invention is furthermore directed to a method for cutting plastic
products
at varying temperatures. More specifically, the invention relates to a method
for
cutting plastic products provided in a continuous band consisting of segments
to be
cut with one laser cut for use in the medical sector, wherein the method
enables
cutting of the plastic products provided in the continuous band at varying
temperatures.
The application WO 2009030311 Al describes a cutting device, for cutting
single
containers provided in a plastic band, characterized by a free falling
mechanical
punching device, which separates by free fall the single containers from the
surrounding material. In another application WO 2009106219 Al the mechanical
punching device is powered by an electro motor, which moves the punching
device
from the starting position in a punching position.
When the plastic products leave the forming mould, they usually have to be
cooled
down, before separation from the surrounding residual material is possible.
During
the cooling process the plastic products are subject to temperature dependent
changes in their size (shrinking). Thus, the prior art mechanical punching
devices are
dependent on a predetermined temperature, at which the plastic products can be
separated, because only at this temperature does the size of the plastic
products in
the continuous band correlate with the shape of the punching tool. This means,
that
the mechanical punching device is positioned in a fixed distance from the
plastic
products manufacturing device, e.g. a Blow-Fill-Seal apparatus, so that the
plastic
products have an exact predetermined temperature, when they reach the
mechanical
punching device. However, if any inconsistencies, small deviations, and/or
delays in
the manufacturing process occur, than the plastic products no longer have the
required temperature and thus the calculated size of the plastic products is
no longer
given. In consequence, the following mechanical punching inevitably causes
damage
and/or destroys the plastic products, while they are punched "out" from the
surrounding residual material. Thus, almost all state of the art mechanical
cutting
devices for plastic products used in the medical field work at room
temperature
where the plastic product manufactured at higher temperatures has been
completely
chilled so that there is no variation in size anymore. If a mechanical cutting
process
is carried out at elevated temperatures, mechanical cutting devices require
the feed
of interconnected plastic products to be cut which have almost identical
temperature
due to the fact that change of temperature of the plastic products will cause
a change
in their geometry and size. The mechanical cutting devices are not able to
follow
these changes in geometry and size so that cuts at different temperatures will
cause
inaccurate or faulty cuts, thereby producing unrectifiable rejects. Therefore
a
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22
method is needed which is able to cut out plastic products of a segment of
interconnected plastic products at any temperature or any temperature range
between 30 C and 155 C.
Thus, the further objective of the present invention is to provide a method
for cutting
plastic products or cutting segments of plastic products provided in a
continuous
band for use in the medical sector, wherein the method enables cutting of the
plastic
products or segments thereof provided in the continuous band at varying
temperatures.
This objective is achieved by a method for cutting as described herein.
Further
preferred embodiments are described herein.
Consequently, a method is provided for cutting plastic products for use in the
medical
sector provided in a continuous band of plastic consisting of segments to be
laser
cut, comprising the following steps:
a) Providing interconnected plastic products embedded in a continuous band
of plastic consisting of segments to be laser cut, wherein each segment
cools-down while being laser cut and has any temperature range when
being cut within 30 C to 155 C,
b) Determining positional data for the interconnected plastic products
embedded in the continuous band of plastic in one segment through an
optical acquisition unit and calculation of a cutting pattern through a data
processing unit,
c) Controlling the laser by means of a laser control system, consisting of a
controllable focusing optic, a controllable deflection means and a beam-
forming means, wherein in dependence of the determined positional data
the position and intensity of the focal point of the at least one laser is
controlled,
d) Laser cutting the interconnected, cooling down plastic products, provided
in a continuous band of plastic in one segment according to the calculated
cutting pattern.
Therefore, the inventive method is useful for cutting warm or hot polymers and
plastics, i.e. cutting polymers or plastics with a temperature of at least 30
C,
preferred at least 60 C, preferred at least 80 C, further preferred at least
100 C,
more preferred at least 115 C, more preferred at least 125 C, even more
preferred at
least 135 C, further preferred 145 C and more preferred at least 155 C,
whereby
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plastics and/or polymers can be cut even at temperatures from 200 C to 250 C.
Thus, at the beginning of the laser cut, the temperature of the segment has at
least
one of the above described temperatures.
In further embodiments at the beginning of the laser cut the segment has any
temperatures ranging from 30 C to 155 C, preferably from 35 C to 125 C, more
preferably from 40 C to 110 C, still more preferably from 45 C to 100 C, still
more
preferably from 50 C to 90 C and most more preferably from 55 C to 80 C.
Thus, the inventive method allows the cutting of plastic products provided in
a
continuous band or within segments of the continuous band at any temperature
and
is totally independent from any changes in size of the plastic products due to
shrinkage, e.g. while cooling down. Depending on the form and size of the
plastic
products, the exact type of plastic used and several other factors, the
temperature of
the plastic products can vary, which makes mechanical punching at a
predetermined
temperature only possible for very narrow applications, namely only one fixed
manufacturing process for one product. Each change in one of these parameters
inevitably necessitates a rearrangement of the manufacturing line, which does
not
only comprise the changing of the punching mould itself but also includes the
repositioning of the whole punching device. This could be the case, when
another
type of plastic is used, which has a higher processing temperature and thus,
has to
cool for a longer period of time before mechanical punching is possible. In
some
instances it could not even be possible to rearrange the manufacturing line,
because
of only limited space available. Without the need for changing of punching
moulds,
rearrangement of the manufacturing line and the installment of a long cooling
line,
the provided method has a much greater flexibility, is more economically and
saves a
lot of space.
The term "interconnected plastic products provided in the continuous belt" is
to be
understood as an endless belt with a defined width, wherein the interconnected
plastic products are embedded, i.e. are surrounded by the residual material.
The term "segment" is to be understood as the section for example in a
continuous
belt that is recognized in one single work cycle by the optical acquisition
unit and
were the cutting pattern is defined. Thus, a "segment" has a defined length
and
width, with a certain number of interconnect plastic products. Consequently,
the
proportions of the segments are directly dependent from the settings of the
optical
acquisition unit. The term "segment" is not to be understood in a physical
sense in
that there are e.g. precut fields or markings in the continuous belt, but is
solely
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defined by the field of acquisition from the optical acquisition unit. A
"segment" is
preferably this part of the continuous band which is detected or picked by the
optical
acquisition and data processing unit in one work cycle and which preferably
contains
a certain number of interconnect plastic products.
However the subdivision or
partition of the continuous band into segments is a more theoretical construct
due to
the fact that the continuous band does not contain markers indicating the
segments
and due to the fact that the position of the segments can be selected
arbitrarily.
Moreover it is possible that two segments overlap or that two subsequent
segments
are not directly connected to each other.
Accordingly, with the inventive method it is possible to cut one segment,
which has a
certain temperature and directly cut a subsequent segment, which can have
another
temperature. Thus, each segment can be cut precisely independent from its
temperature and the temperature of the previous or the following segment with
plastic products in the continuous band. With a mechanical punching device,
such
precise cutting at varying temperatures is not possible. The plastic products
would
have different sizes due to the different temperatures and thus cannot be
punched
mechanically.
Thus, the method according to the invention is preferably used to cut plastic
products
that are in the process of cooling or heating, wherein the temperature of the
segment
to be cut is different at the beginning of the cutting process in comparison
to the
temperature at the end of the cutting process. The laser cutting is very
accurate even
when a temperature gradient exists, i.e. temperature changes during cutting in
the
plastic product or the plastic segment respectively. The cutting pattern for
the plastic
products can be acquired and processed correctly in a temperature range from
¨ 30 C to + 300 C and preferably from + 30 C to + 300 C. Any changes in the
temperature of the plastic up to 1 C per second can be acquired and processed.
This
includes also changes in consecutive cutting patterns and cutting modes as
well as
for changing plastic materials during the cutting of a cutting pattern or for
consecutive
segments and cutting patterns.
Consequently, in one embodiment at least one segment with interconnected
plastic
products has a varying temperature than any of the previous segments with the
interconnected plastic products. The term "varying temperature" is to be
understood
to comprise any differences in temperature that exceed at least 0.5 C. This
is
particularly advantageous, if it comes to delays and/or small inconsistencies
during
the manufacturing process. In such cases it is still possible to cut the next
segment
with interconnected plastic products that are provided in the continuous belt,
even
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though the size of the plastic products has changed due to the extra cooling
time.
Thus, with the inventive method it is preferred to cut interconnected plastic
products
provided in the continuous belt that have a cool-down rate of 0.01 C to 5 C
per
minute. In a preferred embodiment the interconnected plastic products provided
in
the continuous belt consist of polypropylene and/or polyethylene.
In another embodiment incomplete or incorrect cut segments are re-fed and then
cut
again at a lower temperature. Incomplete or incorrect cut segments are usually
thrown away, because it was not possible to cut these segments again, as these
segments had cooled down completely and would no longer fit in mechanical
punching machines that are configured to punch segments with a higher
temperature. With the inventive method these segments can be re-fed and then
cut
accordingly.
The inventive method can be performed with a device comprising at least one
laser,
at least one laser control system, at least one optical acquisition and data
processing
unit, and optionally a quality control device with an integrated pressure
sensor for the
detection of incorrect laser cuts.
The optical acquisition unit determines in a segment positional data of the
plastic
products provided in the continuous band and connected to each other. The
positional data in the segment are used to calculate a cutting pattern, which
is
transmitted to the laser control system. In accordance to the cutting pattern,
the
position, intensity and focal point of the at least one laser beam is
controlled through
a focusing optic and a deflection means.
Accordingly, gas lasers, solid-state lasers and/or dye lasers can be used. The
lasers
belonging to the group of gas lasers comprise excimer laser, noble gas ion
laser,
metal vapor laser or molecular gas laser.
The group of excimer lasers includes but is not restricted to H2-laser
(116/123 nm),
Ar2-laser (126 nm), F2-laser (157 nm), Xe2-laser (172 nm), ArF-laser (193 nm),
KrF-
laser (248 nm), XeBr-laser (282 nm), XeCI-laser (308 nm) and XeF-laser (351
nm).
Noble gas ion lasers include but are not restricted to (Ar)-laser (including
¨460 nm,
480 nm, 500 nm, 520 nm), (Kr)+-laser (650 nm) and He-Cd-laser (325 nm, 440
nm).
The group of metal vapor lasers includes but is not restricted to Cu-laser
(500 nm,
545 nm) and Au-laser (310 nm, 605 nm). The group of molecular gas lasers
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comprises CO-laser (6-8 pm), CO2-laser (9 pm, 10.6 pm, 11 pm) and N2-laser
(337
nm).
Solid-state lasers can be selected from ruby Cr3+:A1203-laser (694 nm),
Neodymium
glass (Nd:Glass) laser (1062 nm), Neodymium-YAG-laser (1064 nm), Alexandrite-
laser (755 nm), ALGaN/GaN-laser (400-500 nm), InGaAs/GaAs-laser (700-880 nm),
InGaAsP/InP-laser (900-1100 nm) and Pb-Chalkogenide-laser (2,6-30 pm). The
group of dye lasers comprises amongst others stilbenes, coumarins and
rhodamines
covering the whole spectrum from -300 nm to 1300 nm.
In further embodiments the cutting process or the laser cut can be performed
parallel,
synchronous or consecutively by multiple lasers. Preferably the cutting
process or the
laser cut is performed by two lasers, more preferably by three lasers and most
preferably by four lasers. There is no limit to the number of lasers. The
number of
lasers can be adapted and depends on the complexity of the cutting pattern and
the
size and dimension of the plastic products provided in the continuous band. It
is also
possible to split the laser beam with a beam splitter into multiple beams and
control
each beam independently from each other for the cutting process. Preferred are
CO2-
laser and UV-laser. In particular preferred are CO2-laser with a wave length
of
9.4 pm, more preferably with 10.3 pm or 10.6 pm with a preferred output power
of
200 W or between 180 W and 220 W respectively. Preferred UV-laser comprise
solid-state lasers on the basis of Nd:YAG, YLF or Nd:VO4, where by means of
frequency conversion with nonlinear crystals, the third harmonic with a
wavelength of
355 nm or in the vicinity thereof is generated. These lasers enable an
extremely fine
focusing of the laser beam, which is suited to cut or separate or perforate
the narrow
connections between the plastic components completely or partially.
According to the inventive method, a focused laser beam is guided around the
contours of the plastic products in the segment provided in the continuous
band to
melt or evaporate the material between the products and/or the continuous
band.
The Gaussian intensity distribution of the laser beam cross-section ensures
that the
laser radiation melts the material at the edges and no burr formation occurs.
This has
the advantage that at the edge of the plastic products no sharp edges form
that may
damage e.g. sterile gloves used in the medical field or even lead to cuts to
the hand
of the person working with the cut plastic products. The separation with a
laser beam
has distinct advantages over mechanical separation devices like e.g. punching
devices, because the use of mechanical devices leads inherently to the
formation of
burrs or sharp edges. The sharpness of the resulting burr and/or the cutting
edge is
directly dependent form the hardness/rigidity of the plastic material.
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The plastics are preferably selected from the group consisting of polyamides,
polyolefins or copolymers, as well as combinations of such plastics or
copolymers in
the form of composite materials. Preferably the plastic is polyethylene (PE),
even
more preferred is polypropylene (PP) or any other plastic with at least the
hardness/rigidity, tensile strength, torsion module, Young's modulus and/or
melting
range of polypropylene (PP). Any plastic, that is at least as rigid or hard or
even more
rigid or harder as PP can be cut preferably according to the present
invention.
The laser cut of the segment or the laser cutting of PP is performed at any
temperature between 30 C to 155 C, preferably between 35 C to 125 C, more
preferably between 40 C to 110 C, still more preferably between 45 C to 100 C,
still
more preferably between 50 C to 90 C and most more preferably between 55 C to
80 C.
Further plastics that can be used can be selected from the group consisting of
or
comprising: polyvalerolactones, poly-c-decalactones, polylactonic acid,
polyglycolic
acid, polylactides, polyglycolides, copolymers of the polylactides and
polyglycolides,
poly-c-caprolactone, polyhydroxybutanoic acid,
polyhydroxybutyrates,
polyhydroxyvalerates, polyhydroxybutyrate-co-valerates,
poly(1,4-dioxane-2,3-
diones), poly(1,3-dioxane-2-ones), poly-p-dioxanones, polyanhydrides such as
polymaleic anhydrides, polyhydroxymethacrylates, fibrin, polycyanoacrylates,
polycaprolactonedimethylacrylates, poly-b-maleic acid, polycaprolactonebutyl-
acrylates, multiblock polymers such as from oligocaprolactonedioles and
oligodioxanonedioles, polyether ester multiblock polymers such as PEG and
polybutyleneterephtalate, polypivotolactones, polyglycolic acid trimethyl-
carbonates,
polycaprolactone-glycolides, poly-g-ethylglutamate, poly(DTH-iminocarbonate),
poly(DTE-co-DT-carbonate), poly(bisphenol-A-iminocarbonate), polyorthoesters,
polyglycolic acid trimethyl-carbonates, polytrimethylcarbonates,
polyiminocarbonates,
poly(N-vinyl)-pyrrolidone, polyvinylalcoholes, polyesteramides, glycolated
polyesters,
polyphosphoesters, polyphosphazenes,
poly[p-carboxyphenoxy)propand
polyhydroxypentanoic acid, polyanhyd rides, polyethyleneoxide-propyleneoxide,
polyurethanes, polyether esters such as polyethyleneoxide, polyalkeneoxalates,
polyorthoesters as well as copolymers thereof, carrageenanes, collagen,
polyhydroxyalkanoates, pectic acid, actinic acid, carboxymethylsulphate,
collagen,
collagen-N-hydroxysuccinimide, polyacrylic acid,
polyacrylates,
polymethylmethacrylate, polybutylmethacrylate, polyacrylamide,
polyacrylonitrile,
polyamides, polyetheramide, polyethylene amine, polyimides, polycarbonates,
polycarbourethane, polyvinyl ketones, polyvinyl halides, polyvinylidene
halides,
polyvinyl ethers, polyvinyl aromatics, polyvinyl esters, polyvinylpyrrolidone,
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polyoxymethylene, polybutylene, polytetrafluoroethylene, polyolefin
elastomers,
polyisobutylene, EPDM Rubber, Fluorosilicone, carboxymethylchitosan,
polyethylene
terephthalate, Polyvalerate, ethyl vinyl acetate copolymers, polysulfones,
polyethersulfones, epoxy resins, ABS resins, silicones such as polysiloxanes,
Polyvinylhalogene and copolymers and / or mixtures of the aforementioned
polymers
as well as laminates and multi-layer systems of the aforementioned polymers.
Plastic products made of polypropylene have the great advantage over plastic
products made of polyethylene that they can be autoclaved and sterilized at or
above
temperatures of 121 C. This is of particular importance in the medical sector,
where it
is essential to ensure that all germs are killed. Because of the higher
temperatures
necessary to process polypropylene the plastic products have to be cooled down
over a longer distance and/or a longer time before it is possible to cut the
plastic
products out of the continuous plastic band wherein the single plastic
products are
connected to each other. Moreover, PP is much harder than PE and mechanical
cutting or punching leads naturally to even more sharp burrs and/or cutting
edges.
With the inventive method it is possible to cut plastics, especially PP with a
high
processing temperature directly after processing. It is not necessary to wait
for the
plastics to cool down nor is it needed to install long conveyer bands to cool
the
plastic products during transportation down to a temperature at which it is
possible to
cut the plastic products. Consequently, it is also preferred to cut plastics
that have a
high Young's modulus and thus tend to form sharp burrs and/or edges when cut
or
punched mechanically. Especially preferred is polypropylene, which is
regularly
specified with a melting range between 160 C and 170 C and a Young's modulus
of
about 1520 N/mm2. Thus, such plastics are preferred which have a melting range
above 160 C, more preferred above 180 C, further preferred above 200 C and
especially preferred above 220 C and can be routinely autoclaved at or above
temperatures of 121 C without getting deformed. Furthermore, such plastics are
preferred which have an operating temperature above 100 C, more preferred
above
110 C and/or with a Young's modulus above 1500 N/mm2, more preferred above
1700 N/mm2 and further preferred above 1900 N/mm2. An especially preferred
plastic
that can be cut with the inventive device is polypropylene and any other
plastics,
characterised by a melting range, tensile strength, torsion module or
hardness/rigidity
in the range of polypropylene, wherein "in the range" of is defined as 10%
to the
corresponding value of polypropylene, i.e. a value of -10% to +10% of
polypropylene.
The inventive method uses a laser to cut the plastic products provided in the
continuous band of plastic. A cooling line for the hot plastic products is not
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necessary, because the laser can cut the hot material or the hot material in
the
process of cooling down respectively, safely and precisely. This is especially
advantageous, when cutting plastic products for the medical sector at elevated
temperatures directly or shortly after the plastic products leave the molding
roll, when
they already start to harden. Additionally, it is possible to perforate the
narrow
connections between the plastic components completely or partially or to
induce
predetermined breaking points making it easier to separate the plastic
products from
each other. This is especially advantageous when the plastic products are made
of
polypropylene, which is extremely tenacious after cooling down making it
difficult to
separate the plastic products manually without any further mechanical aid e.g.
a
scissor.
The term "cutting" or "laser cutting" as used herein shall be understood as
cutting
through plastic material with a laser beam, preferably polypropylene and
similar
polymers or polyethylene, this also includes perforating, i.e. alternating
parts of cut
through and uncut parts as well as cutting partially through or thinning
parts, in the
meaning that the material at the cutting point is not completely cut through
but only
the thickness is reduced, i.e. the material bonding still exists, but can be
separated
mechanically with less force. Thus, the term "cutting" or "laser cutting"
describes
cutting completely through the plastic material along the whole cutting
pattern or only
at specific points of the cutting pattern as well as perforating the plastic
material
along the whole cutting pattern or only at specific points of the cutting
pattern, i.e.
completely cut through parts alternate with uncut parts. Preferably the term
"cutting"
or "cut" or "laser cut" is to be understood as the cutting done in one segment
of the
continuous belt. After the cutting has been done in one segment, the next
cutting in
the subsequent segment is performed. Thus, each cutting pertains to one
segment,
and each segment starts a new cutting process named as the "cut" or the "laser
cut".
The term "cutting pattern" is to be understood as the totality of all parts to
be cut,
which are acquired by the optical acquisition unit in one detection step/work
cycle.
The cutting pattern can be positioned in a segment of a continuous band of
interconnected plastic products. Thus the term "cutting pattern" refers to the
entirety
of single cut-lines within one segment. Thus, if it is intended to cut plastic
products in
a continuous band or belt of interconnected plastic products, the optical
acquisition
unit gradually acquires a part (i.e. segment) of the continuous band or belt
of
interconnected plastic products, which is fed to the inventive device and then
is cut
according to the cutting pattern. The cutting pattern comprises the plastic
products,
acquired through the optical acquisition unit, which are usually three-
dimensional and
lie above and below the plane level and are defined through the continuous
band or
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the continuous belt, which can comprise further user definable and thus
predefined
information concerning the cutting mode. The optical acquisition unit can
detect for
example, where the cutting is to be performed. The mode of cutting
(completely,
partially, perforating, etc.) can be predetermined by the user. Alternatively
or
additionally the optical acquisition unit can detect respective markings,
which do not
only give information where the cuts are to be made but also the mode of
cutting can
be included as information. Naturally a combination of the aforementioned is
possible, thus a mix of predefined patterns and automatic detection of the
cutting
mode and/or cutting pattern is possible. Instead of a continuous band or a
continuous
belt it is also possible that single units or only parts of the continuous
band, i.e.
isolated segments, are detected by the optical acquisition unit.
The cutting pattern and eventually the cutting mode is determined anew by the
optical acquisition unit for each segment, thus it is possible to handle
various cutting
patterns and cutting modes in random order. This is a distinct advantage over
mechanical cutting and/or punching processes. The mechanical punching or
mechanical cutting tool are determined for a defined cutting pattern or
defined cutting
mode and cannot adapt to changes in alternating segments with different
cutting
patterns and cutting modes. The laser cutting device can handle up to ten
different
cutting patterns with different cutting modes, which is impossible to achieve
with a
mechanical cutting or punching tool. Even if different punching or cutting
tools are
used, there are still only a limited number of patterns that can be handled.
The device
is independent of the exact cutting pattern, i.e. is not restricted to a
specific pattern
but can detect and handle any cutting pattern.
The cutting pattern is determined through suitable markings, which are
detected by
the optical acquisition unit. This can include colored markings, spatial
markings as
well as radioactive markings.
Colored markings include for example, colored markings in the visible range,
infrared
range or UV range and can be incorporated or attached to the plastic. This
extends
also to other materials which can be incorporated or attached to the plastic
and are
distinguishable from the plastic material such as thin filaments, wires or
micro
particles. Spatial markings on the other hand can be realized as elavations,
dents or
holes in the plastic material. Radioactive markers are radioactive substances
incorporated or attached to the plastic material, wherein a radioactively
labeled
substance or solution in the plastic product may serve as a marker.
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The data processing unit determines which parts of the cutting pattern are to
be cut
by the laser completely, or are only perforated, thinned and/or are not to be
processed. Thus, the laser is capable of cutting specific parts completely,
perforate
them, reduce the thickness of the material to a specific degree and/or ignore
specific
parts, all within the limits of the detected and/or predetermined cutting
pattern by the
optical acquisition unit, depending on which mode of cutting was predefined by
the
user or a marking in the cutting pattern or a segment respectively. The laser
is under
the control of the data processing unit and is guided according to the cutting
pattern
detected by the optical acquisition unit and the predefined cutting mode.
The use of the laser beam for accurate cutting of the plastic products is
dependent
from the optical acquisition unit, which determines positional data of the
interconnected plastic products provided in the continuous plastic band. The
positional data can comprise information about the forms, sizes, shapes,
geometric
forms, laser markings, shadow projection, color recognition, light / dark
zones or
reflections which are detected by the optical acquisition unit.
In a preferred embodiment the optical acquisition unit comprises a camera. In
another preferred embodiment a laser scanner is used together with a detector
to
determine positional data by measuring the interconnected plastic products
provided
in the continuous plastic band. The laser can be diverted by a mirror system
to depict
a complete surface profile of the plastic products.
The positional data are transmitted to a data processing unit, e.g. a
programmable
micro processor, where they are further processed. The term "processed" is to
be
understood in the way that the actual determined positional data is compared
with
positional data stored in the data processing unit. For each combination of
positional
data a cutting pattern is stored in the data processing unit, which is
transmitted to the
laser control system to control the laser.
This has the advantage that a precise dimensional accuracy of the plastic
products
provided in the belt is not required, because the optical acquisition unit
detects the
respective actual state of the plastic products. Particularly for the
manufacture of
plastic products usually high temperatures are used. The resulting temperature-
dependent expansion and/or shrinking of the plastic has made an e.g.
mechanical
punching only possible at fixed lower temperatures. The use of the inventive
method
eliminates this problem and the plastic products can be cut accurately at
different and
varying temperatures. Moreover, it follows that when cutting various different
plastic
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products, a complicated conversion of the device is not necessary, because
only the
cutting patterns must be changed for the positional data.
In another preferred embodiment the positional data are not compared with the
i stored positional data, but the data processing unit calculates the
respective cutting
pattern from the acquired positional data and transmits the calculated cutting
pattern
to the laser control system to control the laser.
In a further preferred embodiment positional data as well as cutting patterns
are
I stored, which are corrected by the respective actual positional data,
leading to an
adapted cutting pattern which is transmitted to the laser control system to
control the
laser.
The laser control system consists preferably of a controllable focusing optic,
a
controllable deflection means and a beam-forming means. In this context the
term
"controllable" is to be understood that the focusing optic and the deflection
means
can be controlled with the cutting patterns calculated by the data processing
unit and
further that the data are transmitted in a suitable format. The beam-forming
means
collimates the laser beam and reduces the divergence of the beam for the
purpose of
a better focusing. In accordance with the determined positional data, the
position of
the focus and intensity of the focal point of the at least one laser is
controlled by a
controllable focusing optic and a controllable deflection means. If more than
one
laser is used preferably each laser is controlled by another laser control
system.
In an embodiment the laser control system comprises a beam-forming means,
which
collimates the laser beam, a telescopic lens system, which reduces the
divergence of
the beam for the purpose of a better focusing, a mirror deflection system,
which
guides the laser beam in two- or three-dimensions around the interconnected
plastic
products according to the predetermined cutting pattern, a focusing optic,
which
focuses the laser beam such that the plastic material is evaporated during the
movement of the laser beam and a software-controlled electronics, which
converts
the data for the cutting pattern in mirror movements.
In a preferred embodiment, the controllable deflection means is a galvanometer
scanner, deflecting the direction of the laser beam with mirrors. In more
preferred
embodiments, the galvanometer scanner deflects the laser beam over two or more
mirrors. Depending on the geometric properties of the plastic products one or
more
controllable deflections means can be used. In a preferred embodiment, no
relative
movement takes place between the plastic product and the laser optics, i.e.
the laser
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optics is fixed and immovable, and the laser beam is controlled only by the
controllable deflection means.
In another embodiment the laser beam is not deflected by a controllable
deflection
means, but the laser optics or a part of the laser optics is moved relative to
the plastic
product to perform the cutting process. The term laser optics comprises all
the
components necessary for forming, focusing, controlling or amplifying the
laser
beam. For example, only the lens and the mirror system can be moved, or only
the
lens, or only the mirror system or the entire laser optics relative to the
plastic product.
In a particularly preferred embodiment the laser beam is controlled by a
movable
controllable deflection means. The term movable in this context means that the
controllable deflection means can be moved in the x, y and z axis. This
ensures that
the laser beam can also reach and cut areas which are difficult to access.
A further advantage is that the controllable deflection means can also be used
to
simultaneously label the ampoules, thus cutting and labeling is done in one
work
process.
The focusing optic is preferably a lens or a mirror, more preferably a convex
lens or a
focusing concave mirror. The concave mirror provides the further advantage
that
each laser wavelength can be focused on the same point without having to use
special optical materials.
In one embodiment, the device comprises a conveying unit for the
interconnected
plastic products provided in the continuous band. This conveying unit consists
preferably of a feeding-in device that pulls the interconnected plastic
products
provided in the continuous band under the laser and the optical acquisition
unit. This
allows a high throughput and a full automatic cutting of the plastic products
provided
in the continuous band. Moreover incompletely or faulty cut segments of the
continuous band could be introduced into the laser cutting process again in
order to
complete cutting. The re-introduced segments have further cooled down or
cooled
down to room temperature before they were re-introduced into the cutting
process.
However the inventive method is able to complete the incorrect or faulty laser
cut
within these segments even at quite different temperatures in comparison to
the
temperatures where the original incorrect or faulty laser cut was performed.
The
rejects are detected anew by the optical acquisition and data processing unit
and the
laser-cut is repeated without the need to adjust the complete device to the
new
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temperature of the rejects and without the need to warm the rejects up to
temperatures where the original laser cut was performed.
In other embodiments the conveying unit is a conveyor belt on which the
interconnected plastic products are transported.
One of the significant advantages of laser separation of plastic products,
e.g.
ampoules, bags or other cavities is to create a fused edge as opposed to a
sharp
ridge after mechanical separation. This is especially important when cutting
plastic
products for use in the medical sector because a sharp ridge may cause damage
to
sterile gloves or may even injure the hand of the doctor or of the hospital
staff when
using such ampoules. Mechanically cut plastic products have always sharp
ridges
due to the fact that at the side where the cutting blade leaves the cut line a
sharp
ridge will occur.
The conventional laser cutting process with a fixed beam and focusing through
a
nozzle for processing gas may also lead to burrs on the edges. It is better to
cut the
ampoules with a movable beam, e.g. with a galvo scanner, because this method
can
be carried out more precisely by fine tuning of laser parameters and beam-
forming
elements, such as telescopes and lenses and scanner movements so that the
edges
are fused at the joints. To achieve this, a sensor and a control system are
required
as.
However, even with this kind of separation it is possible that the cut plastic
products,
e.g. ampoules, are not separated with fused edges. This is the case when a
barely
perceptible sharp ridge holds the ampoules together. When the ampoules are
then
finally separated, the sharp ridges still remain. Such sharp ridges can be the
result of
slight power fluctuation of the laser or a barely detectable variation in the
beam
direction.
Since the ampoules are provided within a pack of ampoules with very narrow
connections, the quality of the laser cut can usually only be evaluated with a
very
complex image recognition system and special cameras. Such a system slows down
the whole manufacturing process, is inherently expensive and prone to
malfunctions
and cannot easily be integrated in existing systems.
In another embodiment of the invention, the laser cutting device can
optionally
comprise a quality control device with an integrated pressure sensor for
pressing out
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the cut plastic products. The interconnected plastic products provided in the
continuous plastic band are preferably not separated completely by the laser
from the
residual material, i.e. the framework, so that the cut plastic products can be
transported within the surrounding material until the final separation takes
place.
During the laser cutting, precisely defined narrow connections are left
between the
plastic products and the surrounding residual material. For the final
separation step
the plastic products are transported under the quality control device with an
integrated pressure sensor. A stamp with the form of the ampoule pack or a
stamp
with a certain number of pins which hit predefined locations of the single
plastic
product or of a section of the continuous plastic band, i.e. an adapted stamp,
presses
the plastic products and especially the material between the toggle parts of
the
ampoules, i.e. the material between the neck regions of neighboring ampoules,
out of
the residual surrounding material. If the pressure or force necessary to push
the
ampoules out of the surrounding material and/or the material between the
toggle
regions exceeds a predefined first adjustable value, this is an indication
that the
plastic products are not sufficiently separated and are still connected with
the
surrounding material, i.e. are still connected to the belt or to each other.
Instead of a stamp which actually hits the plastic products or units or
bundles of
plastic products in order to separate them, a gas blow such as an air blow or
multiple
gas blows generated by one or a plurality of nozzles can be used to put a kind
of gas
blow pressure on the plastic products or units or bundles of plastic products.
Thereby the single gas blows are generated with a defined pressure which again
indicates the quality of the laser cut by determining if the gas blow or the
gas blows
were sufficient to separate the single plastic products or units or bundles of
plastic
products. Instead of a gas the skilled person may also use a liquid such as
water for
the same purpose.
Thus, the quality control device with an integrated pressure sensor is
directed to
pressing the laser cut plastic products out of the surrounding residual
material of the
continuous band thereby generating single plastic products or units of plastic
products which are still attached to each other but already perforated
preferably by
the laser used in the cutting device so that the separation can be done easily
without
forming sharp ridges. This is usually performed with an adapted mould having
the
form of the ampoule or ampoule packs. Additionally, narrow stamps can be
included
that push out the residual material between the toggle parts, i.e. the area
between
the neck regions of two adjacent ampoules. If a predefined first adjustable
value is
exceeded, then the laser cutting was not sufficient and the plastic products
are
collected separately. This has the advantage that insufficiently cut plastic
products
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can be separately collected from the correctly cut plastic products and then
proceeded later again and thus are not lost as waste. Thus in one embodiment
the
quality control device with an integrated pressure sensor consists of a mould
adapted
to the form of the ampoules, which presses the plastic products precisely out
of the
surrounding residual material.
Furthermore, the quality control device with an integrated pressure sensor can
control the quality of the laser cut, i.e. the quality of the intended
separation, by
measuring the resistance and/or force that is necessary to press the plastic
products
out of the surrounding residual material. The pressure/force necessary to push
the
ampoules out of the surrounding material and/or the toggle parts of the
ampoules, i.e.
the material between the neck regions of neighboring ampoules, gives direct
information on whether the laser cut did successfully melt the material at the
edges
so that no sharp burr formation has occurred.
The applicant has found when laser cutting, for instance, polypropylene
ampoules
that the following applies:
= If the pressure sensor does not register any resistance, the ampoules are
separated correctly and the edges are completely fused around the ampoules
= If the pressure sensor registers a resistance up to 0.5 N to push the
ampoules
out of the surrounding residual material, then only a negligible ridge has
formed and the use of the ampoule is safe.
= If the pressure sensor registers a resistance over 0.5 N to push the
ampoules
out of the surrounding residual material, then a significant sharp ridge has
formed and the ampoules are possibly harmless and will be sorted out.
Thus, if the required pressure necessary to push the plastic products such as
bags,
bottles, cylinders, ampoules or other cavities out of the surrounding material
and/or
the toggle parts of the ampoules, i.e. the material between the neck regions
of
neighboring ampoules exceeds a second threshold but is still under the first
threshold, this gives an indication that the laser cut is unsatisfactory and
potentially
harmful formation of sharp ridges or burrs in the plastic product has
occurred.
In a further embodiment, the quality control is performed at the material
between the
toggle parts, i.e. the area between the neck regions of two adjacent ampoules.
Thus, the force required to push the plastic products out of the surrounding
residual
material provides information on whether the plastic product was cut
correctly, i.e. the
plastic products can be pushed out of the surrounding material or not.
Furthermore,
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the required force indicates, whether the ridges are safe or if any sharp
ridges have
formed that may be potentially harmful.
Having described quality control device with an integrated pressure sensor it
is clear
i to the skilled artisan that the exact first and second values or
thresholds for the
pressure/force depend on factors such as the kind of plastic to be cut, the
thickness
of the material, the temperature at which the cut is performed, the output
power for
the lasers and/or the geometry or size of the plastic products and the like.
It is within
the scope of the skilled artisan to determine through minimal experimentation,
which
I pressure or force threshold is indicative for the plastic products in the
continuous
band. Thus, it is not complicated and even not inventive to find the right
pressure
range which indicates for the given plastic product a faultless cut or an
inacceptable
cut so that adjustment of the laser has to be performed.
In another embodiment, the quality control device with an integrated pressure
sensor
determines the quality of the laser cut by applying an underpressure to the
plastic
product, such as the ampoule, the ampoule pack and/or the toggle region, i.e.
the
material between the neck regions of the ampoules. The mode of action is
similar to
the above described embodiment, however, it is not the force measured that is
required to separate the ampoule, the ampoule pack and/or the toggle region
from
the surrounding residual material. Instead the quality control device with an
integrated pressure sensor measures the force required to apply a certain
under-
pressure such as a certain vacuum.
While the pressure or force is applied from the above to the upper side of the
single
plastic products or the pack or bundle of plastic products, the underpressure
or
vacuum is applied from below the single plastic products or the pack or bundle
of
plastic products in order to separate the single plastic products or the pack
or bundle
of plastic products from the continuous plastic band and from the other single
plastic
products or the other packs or bundles of plastic products.
In a third embodiment the quality control device with an integrated pressure
sensor
applies a pulling force which can be determined in order to assess quality of
the laser
cut. Such a pulling force can be applied through means which grip the single
plastic
products or the pack or bundle of plastic products and separate them from the
continuous plastic band and from the other single plastic products or the
other packs
or bundles of plastic products. The force required to separate the single
plastic
products or the pack or bundle of plastic products can be measured and is also
an
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indication for the quality of the laser cut in order to assess if the laser
cut was
faultless or not sufficient.
Consequently, it is not important if the separation of the single plastic
products or the
single packs or single bundles of plastic products is conducted by a pushing
force
such as pressure, or a pullin force or an under-pressure such as vacuum.
In a further embodiment, the device comprises a system to compensate for long-
term
drift effects of the laser beam and the controllable deflection means. This
may occur
due to changes in temperature, humidity, exposure to vibration, mechanical
stress
and aging of components and can affect the precision of the laser beam
negatively.
The system to compensate for long-term drift effects of the laser beam ensures
that
the precision of the laser is always optimal, reducing production losses, due
to
maintenance of the device, to an absolute minimum.
In one embodiment, a thermal imaging camera is used, to register the selective
heating on a material surface lying outside of the cutting pattern, but still
within the
range of deflection of the mirror system of the controllable deflection means.
The
selective heating results by directing the beam for a short time on this
material
surface for a specific length of time. These short-term heating can for
example be
performed while the feeding-in device pulls the next interconnected plastic
products
provided in the continuous band under the laser and the optical acquisition
unit. The
thermal imaging camera compares the position on the receiver with previously
programmed set/designed positions. The data collected is then transmitted to
the
laser control system to correct and adjust the cutting pattern. This control
mechanism
can take place both in or before each cutting process or at certain predefined
intervals. The thermal imaging camera can also determine simultaneously the
temperature of the heated material surface and conclude from this data on the
laser
power used for cutting the plastic products. A decrease in laser power can
then be
adjusted accordingly.
In another embodiment a band lying outside of the cutting pattern, but still
within the
range of deflection of the mirror system of the controllable deflection means,
is drawn
along within or outside of the plastic band, whereby the laser removes an
amount of
the material in the band in the form of a point. A camera compares the
position of this
point with a programmed reference point and any deviations are transmitted as
correction data to the laser control system, similar to the process described
above.
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The interconnected plastic products for use in the medical field provided in
the
continuous plastic band are preferably bottles, bags or containers, and even
more
preferred ampoules. Furthermore, medical devices or parts of medical devices
can
be cut according to the invention, such as syringes, vials, hollow fibers for
dialysators
or parts of powder inhalers.
Particularly advantageous is the use of the method when cutting multi-layer
plastic
products, such as those produced via co-extrusion blow molding. These multi-
layer
plastic products combine the positive properties of different plastics
together and are
usually characterized by a barrier layer that is arranged between two carrier
layers,
which are connected together by a bonding agent. Preferably, these multi-
layered
plastic products are used in applications where improved barrier properties
are
needed to gases. Mechanical cutting methods have particularly problems with
the
joints of the multilayer plastic products. At the joints the barrier layer is
naturally not
very pronounced and there is an increased risk that the barrier layer is
interrupted by
the mechanical cutting in those areas. The inventive method has the advantage
that
the individual layers of the multilayer plastic products are fused together at
the joints
and along the edges during cutting with the laser. Consequently, the barrier
properties of the joints, edges or seams remain intact and are even improved
in
comparison to mechanical cutting methods.
The process for separation of plastic products provided or surrounded by
plastic can
be applied and performed similar in principle with the described laser-control
system
with other plastic products such as consumer goods or industrial parts.
The inventive method is particularly advantageous for cutting plastic ampoules
interconnected, joined together and/or linked together. These ampoules can
e.g. be
filled by the BFS process (blow-fill-seal process) but also empty ampoules can
be
processed. When plastic ampoules are manufactured under the BFS process (blow-
fill-seal process), the ampoules leave the filling machine as rows of
interconnected,
joined together and/or linked together ampoules in a continuous band. In this
continuous band one row of interconnected, joined together and/or linked
together
ampoules is followed by the next row of ampoules and all rows are embedded in
the
continuous band and surrounded by the residual plastic material. In order to
produce
as many ampoules within the continuous plastic band as possible, the ampoules
are
arranged very close together and thus the separation of the ampoules is very
difficult.
This is especially true for the toggle portion at the neck of the ampoules.
The toggle
portion at the neck of the ampoules is a critical area during mechanical
punching as
there is only a very small area that has to be cut out precisely and often
only a partial
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separation can be achieved. Thus there is the constant risk when opening or
separating a single ampoule that the neighbor ampoule is opened accidentally,
due
to the incomplete separation between the toggle portions of the ampoules. The
, inventive method can separate this portion of the ampoules safely without
the risk of
damaging the opening of the ampoules.
Ampoules in the medical field are usually provided as packs, i.e. a certain
number of
interconnected ampoules are punched out mechanically out of the continuous
band.
However, especially ampoules made of polypropylene tend to develop a sharp
ridge
when cut out mechanically or when one ampoule is separated manually from the
ampoule pack.
In contrast to mechanical punching, cutting with the inventive device has the
following advantages. The plastic ampoules are not required to cool down and
can
be cut at higher temperatures. Differences in the size of the ampoules which
are
inherent and cannot be avoided when manufacturing ampoules at high
temperatures
and the shrinking process of the ampoules when cooling down are detected by
the
device and the laser beam is adjusted accordingly. Furthermore, when cutting
with
the laser, the formation of sharp ridges and/or burr formation are avoided and
the
ampoules can be provided by the laser with perforations or breaking points
between
or in the plastic products, making them easier to separate from each other.
In a preferred embodiment the plastic products or packs of plastic products
are cut at
temperatures of the plastic products or packs of plastic products of 30 C to
155 C
In further embodiments the method can further comprise one of the following
steps
e) ¨ e"):
e) Performing a quality test by means of a quality control device with an
integrated pressure sensor, which measures the force required to push out the
cut plastic products or packs of cut plastic products.
e') Performing a quality test by means of a quality control device with an
integrated pressure sensor, which measures the underpressure required to
separate the cut plastic products or packs of cut plastic products.
e") Performing a quality test by means of a quality control device with an
integrated pressure sensor, which measures the pulling force required to
separate the cut plastic products or packs of cut plastic products.
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Thus, by means of the integrated pressure sensor, the force, under pressure,
pulling
force or any other such force is measured, which is required to separate the
plastic
products from the surrounding residual material. A
pressure or force or
underpressure (such as vacuum) below a certain value (e.g. value A) indicates
a
proper and faultless cut without sharp ridges, while a pressure or force or
underpressure above a certain value (e.g. value B) indicates an improper and
faulty
cut so that the plastic products cannot be separated or cannot be separated
easily or
cannot be separated without forming sharp ridges. A
pressure or force or
underpressure between the value A and value B indicates an insufficient cut
where
the plastic products can still be separated but might have sharp ridges.
Depending
on the plastic product, the kind of plastic used and the use of the plastic
product in
medicine, the cut plastic products obtained within the range between value A
and
value B might be sold as proper medical products or might be discard as
unrectifiable
rejects. Moreover depending on the plastic product, the kind of plastic used
and the
use of the plastic product in medicine the value A can be identical or almost
identical
to value B.
In a preferred embodiment, when the force to separate the plastic products
from the
surrounding material reaches a first predefined adjustable value, this
indicates that
the plastic products are still connected to the belt and have not been
separated
successfully, i.e. the force was not sufficient. This also implies that when
this first
threshold or first value has been reached, no further force is applied to
separate the
plastic products. This is important, because if the plastic products are still
tightly
connected to the surrounding residual material, applying an unlimited amount
of force
could lead to damage to the belt and the following plastic products, e.g. by
overstretching the (hot) belt.
Furthermore, it is possible to predefine a second value/threshold which is
under or
below the first value. If the force required to separate the plastic products
from the
surrounding residual material exceeds this second value but is still under the
first
value, the plastic products were separated successfully, but this is an
indication for
an unsatisfactory and potentially harmful formation of sharp ridges or burrs.
If the
required force stays under this second value/threshold, then the quality of
the laser
cut is satisfactory and there is no risk of sharp ridges and/or burrs.
As described above it is clear to the skilled artisan that the exact first and
second
values or thresholds for the pressure/force depend on factors such as the kind
of
plastic to be cut, the thickness of the material, the temperature at which the
cut is
performed, the output power for the lasers and/or the geometry or size of the
plastic
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products and the like. It is within the scope of the skilled artisan to
determine through
minimal experimentation, which pressure or force threshold is indicative for
the
plastic products in the continuous band. Thus, it is not complicated and even
not
inventive to find the right pressure range which indicates for the given
plastic product
a faultless cut or an inacceptable cut so that adjustment of the laser has to
be
performed.
In a preferred embodiment an ampoule belt (1) is pulled and positioned by a
feeding-
in device (2) under at least one controllable deflection means (5) and an
optical
acquisition unit (5a). The optical acquisition unit (5a) acquires in a segment
the
positional data of at least one ampoule strip (II) and the data processing
unit
calculates from the positional data a cutting pattern for cutting the ampoules
(III)
individually or in packs of several ampoules out of the at least one ampoule
strip (II).
The ampoule strip (II) can be named as a segment of the ampoule belt (1). This
segment or ampoule strip (II) has a temperature of 67.5 C when fed into the
cutting
device. When the laser-cut starts, the temperature of the segment or ampoule
strip
(II) is 67.1 C. The at least one focused laser beam (IV) is modified by the
beam-
forming means (4), such that the laser beam is suitable for separating the
ampoules
(III) through evaporation of the material between and/or around the ampoules.
The
controllable deflection means (5) and the controllable focusing optic (5b)
control the
at least one focused laser beam (IV) according to the cutting pattern
calculated by
the data processing unit, to cut the ampoules individually or in packs of
several
ampoules. After the cutting process the ampoule belt (1) is pulled further by
the
feeding-in device (2) and the next ampoule strip (II) is positioned under the
controllable deflection means (5) and the optical acquisition unit (5a). The
cut
ampoules (III) are still located in the ampoule belt (1) and are now
positioned under
the quality control device with an integrated pressure sensor (7) and the
knife for
separating the strips (8). The quality control device with an integrated
pressure
sensor (7) and the knife for separating the strips (8) are triggered and the
separated
material between the toggle parts is collected in a separate container (14).
The
ampoules (III) are now separated completely from the ampoule belt (1) and are
transported in an upright position over a slide to an external transport route
(9) for
further processing. The knife (8) separates the residual material (10) of the
stripe
from the belt and collects the residual material in the container (15). When
the quality
control device with an integrated pressure sensor (7) is triggered to press
the
ampoules (III) out of the belt it simultaneously measures the required
pressure. If one
or more ampoules are not separated as planned, then the required pressure to
press
the ampoules (III) out of the belt exceeds a previously adjustable threshold
value,
whereby the flap (11) is opened and the residual material with the filled
ampoules
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(12) is dropped in the container (16). If the laser cutting device falls out
completely,
then two flaps (13) are triggered and the feeding-in device (2) transports the
residual
ampoule belt (1) uncut out of the device for later cutting. In case the
quality control
device with an integrated pressure sensor (7) detects an insufficient or
inaccurate or
faulty laser-cut of a segment or of an ampoule strip (II), this segment or
ampoule strip
(II) when separated from the ampoule belt (1) which is the continuous band can
be
re-introduced into the laser cutting process and is fed into the cutting
device again.
When feeding this separated segment or separated ampoule strip (II) again,
this
segment or ampoule strip (II) has meanwhile cooed down to 48 C and has shrank.
However the change in size and geometry of the re-fed segment or ampoule strip
(II)
does not effect the second laser-cut. The cutting pattern are newly detected
by the
optical acquisition unit (5a) and the laser-cut is again performed now
resulting in a
properly and accurate cut segment or ampoule strip (II). The properly and
accurate
cut segment or ampoule strip (II) is then processed as usual through the
quality
control device with an integrated pressure sensor (7) without detection of
inaccurate
or faulty cuts.
In another embodiment the inventive device separates container products from a
framework and/or among each other and consists of at least one laser with at
least
one laser control system and at least one optoelectronic system for image
recognition and image processing, which determines the position of the
container
products in the framework and/or among each other and transmits these data to
the
at least one laser control system, whereby the at least one laser and/or laser
beam is
controlled such that the container products are separated from the framework
and/or
among each other. The other described inventive embodiments and examples in
this
application apply advantageously also on this embodiment.
The following examples describe preferred embodiments of the present invention
and
are not to be understood to limit the invention in any way. Any alternatives
and/or
embodiments of the present invention that are natural or obvious for the
skilled
artisan are considered to be defined by the present invention and covered by
the
claims.
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Examples
Example1:
Method for cutting interconnected plastic ampoules provided in a continuous
band:
A camera acquires the positional data for the interconnected plastic ampoules
provided in a continuous band of plastic. The positional data is converted by
the data
processing unit in a cutting pattern for the laser beam. The exact path for
separating
the ampoules with the laser beams is obtained by conversion of a CAD graphics
of
the ampoules, which is transmitted in the form of converted commands to the
laser
beam control system. A beam-forming system, consisting of a lens system for
improving the beam properties (4), modifies the laser beam (6) such that the
beam is
suitable for ampoule separation by evaporation and is also divided in several
beams.
Overall four CO2-laser with an output power of 200W each are deployed. To
improve
the focusing properties of the laser beams, the diameter of the laser beams is
widened and adjusted to the following mirror deflectors. The mirror deflectors
are
dimensioned in such a way that the beam can move freely within the opening of
the
focusing optics after deflection over the necessary deflection range. In this
example
four mirror deflection systems and focusing optics are deployed stationary
next to
each other. The laser beams cut ampoule packs from an ampoule belt with twenty
adjacent ampoules, each pack consisting of five ampoules. As a result of the
ampoule geometrics the laser beams cannot reach the ampoule bottoms in the
same
work step. Consequently, the ampoule bottoms are separated in the previous
work
step. In the current work step the remaining sides of the ampoules packs are
cut and
the bottoms of the next ampoules are cut. The ampoule packs are still
connected by
narrow connecting pieces to the outer framework, however, the single ampoule
packs are separated completely from the adjacent ampoule packs. The material
between the ampoules within a pack is perforated with the laser, which makes
it
easier to separate the ampoules manually.
Example2:
Device for cutting interconnected plastic ampoules for use in the medical
sector
provided in a continuous band:
The belt with the ampoule strips (1) that comes out of the filling machine is
pulled by
means of a feeding-in device (2) in a processing position under the mirror
deflector
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(5). In this position, a digital camera takes an image of multiple reference
markings
and compares the position of these markings with the designed position of
previously
stored reference markings. Thus both the position and the size of the ampoules
is
registered and deviations in size and form due to varying temperatures or
varying
cooling areas within the ampoules or the ampoule strip (1) are corrected and
transmitted for control of the laser beam.
The exact path for separating the ampoules with the laser beams is obtained by
conversion of a CAD graphics of the ampoules, which is transmitted in the form
of
converted commands to the laser beam control system. A beam-forming system,
consisting of a lens system for improving the beam properties (4), modifies
the laser
beam (6) such that the beam is suitable for ampoule separation by evaporation
and
is also divided in several beams. Overall four CO2-lasers with an output power
of
200W each are deployed. To improve the focusing properties of the laser beams,
the
diameter of the laser beams is widened and adjusted to the following mirror
deflectors. The mirror deflectors are dimensioned in such way that the beam
can
move freely within the opening of the focusing optics after deflection over
the
necessary deflection range. In this example four mirror deflections systems
and
focusing optics are deployed stationary next to each other. The laser beams
cut
ampoule packs from an ampoule belt with twenty adjacent ampoules, each pack
consisting of five ampoules. As a result of the ampoule geometrics the laser
beams
cannot reach the ampoule bottoms in the same work step. Consequently, the
ampoule bottoms are separated in the previous work step. In the current work
step
the remaining sides of the ampoules packs are cut and the bottoms of the next
ampoules are cut.
All components necessary for beam formation are connected with enclosed (17)
granite constructions (3) ensuring that no vibration or oscillation is
transferred to the
highly sensitive beam guiding system. A control program for the deflection of
the
movable mirrors guides the focused laser beams along the contours of the
ampoules
such that the ampoules are separated from the residual material save for a
couple of
narrow connections. After this process the feeding-in device (2) pulls the
next
ampoule strip in processing position. The completely or nearly completely
separated
ampoules as well as eventually existing material between the toggle parts is
separated from the residual framework by the quality control device with an
integrated pressure sensor (7) and the ampoules are transported in upright
position
over a slide to an external transport route (9) for further processing,
wherein the
residual material between the toggle parts is collected in a container (14).
The quality
control device with an integrated pressure sensor (7) consists of two
simultaneously
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controlled stamps, wherein one stamp pushes the ampoule pack out and the other
stamp pushes the residual material between the toggle parts. The stamps are
moved
pneumatically, wherein the pressure is adjustable. If the required pressure
exceeds a
first threshold, a sensor is activated, indicating an incomplete separation of
the
ampoules, the sensor then transmits a signal to the sorting device, which
removes
the ampoules. If the required pressure exceeds a second threshold but is still
under
the first threshold, a sensor is activated, indicating an unsatisfactory and
potentially
harmful formation of sharp ridges or burrs in the ampoules, the sensor then
transmits
a signal to the sorting device, which removes the ampoules.
The removed
ampoules are not unrectifiable rejects but can rather be re-introduced into
the
inventive cutting device for repeating the laser cut. Since this re-
introduction can be
done automatically the inventive cutting device or inventive cutting machine
produces
only a few unrectifiable rejects and thus saves costs and material and reduces
waste.
A knife (8) separates the residual material (10) of the stripe from the belt
and the
residual material (10) is collected in a container (15). If one or more
ampoules are not
separated as planned and still are connected to the residual material, e.g.
when the
the quality control device with an integrated pressure sensor transmits a
signal to the
sorting device, a flap (11) is opened and the residual material with the
filled ampoules
(12) is dropped in the container (16). If the laser cutting device falls out
completely,
then two flaps (13) are triggered and the feeding-in device (2) transports the
uncut
belt out of the device for later cutting.
Reference list:
Figure 1
Belt with ampoule strips
II Strips with ampoules
Ill Ampoules
IV Focused laser beam
V Material between the ampoules
VI Residual material / Framework
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Figure 2
1 Ampoule belt
2 Feeding-in device
3 Granite construction
4 Beam-forming
5 Controllable deflection means
5a Optical acquisition unit
5b Controllable focusing optic
6 Laser
7 Quality control device with an integrated pressure sensor
8 Knife to separate the strips
9 External transport route
10 Slide for residual material
11 Flap for not separated ampoules
12 Strips with not separated ampoules
13 Flap for redirecting the complete belt
14 Container for residual material between the toggle parts
15 Container for residual material
16 Container for strips with ampoules
17 Covering hood for the laser beam system
